It is known to couple electrical signals to printed circuit boards by means of permanently mounted connectors fastened and soldered to a surface of the board. Such permanently-mounted connectors include electrically insulative bodies supporting electrically conductive solder tails through which the signals are carried. According to one technique, the connector bodies are positioned and fastened to the board with the solder tails positioned over pads on the surface of the board which are coated with solder paste. The solder paste is then "reflowed," that is, heated. When the solder cools, electrically conductive joints are formed between the solder tails and the pads to conduct signals to and from the board.
The fasteners holding the connector body against the board must perform two tasks. The fasteners must hold the solder tails in position against the pads during solder reflow, and resist board distortion and connector movement so that reliable solder joints form between the tails and pads. The fasteners also provide strain relief to protect the solder joints from breaking due to external forces such as those due to handling.
Proposed fasteners for holding connector bodies against the surface of a printed circuit board include screws, rivets, non-metallic posts and plastic snap fit pegs. One drawback to these styles of fasteners is that, in order to develop sufficient retention force, they must pass through a hole in the board and protrude through the surface opposite that on which the connector body is mounted. For example, one style of non-metallic post is passed through a hole in the surface of the board and "staked," or deformed, to form a plug on the opposite surface. The protrusion of such fasteners through the opposite surface of the board increases the thickness of the board-mounted circuit and limit their usefulness on low-profile applications.
Another proposed style of fastener is a non-metallic post which is press fit into a hole in the board. Unlike those previously discussed, press fit fasteners need not protrude through the opposite surface of the board. Unfortunately, these press fit fasteners require an excessive insertion force which may preclude their insertion by hand tools. Furthermore, such fasteners are very sensitive to tolerance stack-ups between the hole diameter and the fastener diameter. There remains a need for a fastener with sufficient retention force to hold a printed circuit board mounted connector without protruding through the opposite surface of the board or requiring an excessive insertion force.